The notion that mental traits, quite like bodily ones, are transmitted from parents to children is probably as old as mankind. The scientific treatment of the issue starts with Darwin, and ever since the debate about the heritability of mental traits has been going on, often raging on. Probably unforeseen by Darwin the issue is as controversial today as it can possibly be. The debate is particularly heated when dealing with the question whether differences between ethnic groups, with respect to mental traits like intelligence, have a genetic basis. The book tries to address the fundamental problems, both scientific and ideological, that plague the field.